Musical instrument driving circuit for producing percussion sound

ABSTRACT

A driving circuit for producing percussion sound employed in an electronic musical instrument is composed of a plurality of circuit branches each of which consists of a capacitor and a resistor connected in parallel, a diode having the conductivity direction coincident with the charging current into the capacitor, and a normally opened switch interlinked with a corresponding key on the keyboard, all connected in series, the number of the circuit branches being substantially equivalent to the number of the keys on the keyboard, all of the plurality of circuit branches being further connected in parallel, one terminal of thus formed parallel circuit being connected with one end of a power source, the other terminal of the parallel circuit being connected through a resistor to the other end of the power source, whereby, when any one of the keys is depressed and the corresponding switch is closed, a charging current flows into the corresponding capacitor and a trigger signal is obtained from the junction point of the capacitor and the resistor connected to the other end of the power source.

United States Patent [72] Inventor Yasunorillirose Hamamatsu-shi. Japan [21] Appl.No. 819,355 [22] Filed Apr.25, 1969 [4S] Patented ,lan.19, 1971 [73] Assignee Nippon GakkiSeizo KabushikiKaisha Hamamatsu-shi, Shizuoka-ken, Japan [54] MUSICAL INSTRUMENT DRIVING CIRCUIT FOR PRODUCING PERCUSSION SOUND 4 Claims, 2 Drawing Figs. 52 u.s',c| 84/].26 [51] Int.Cl GlOh 1/02 [50] Field of Search 84/l.03,

[56] References Cited UNITED STATES PATENTS 2,989,886 6/1961 Markowitz 84/I.19 3,244,790 4/1966 Sharp 84/l.l3 3,310,622 3/1967 Brand etal. 84/l.l3 3,413,566 Parkyn 84/1.26X

Primary Examiner-W. E. Ray Attorney-Holman, Glascock. Downing & Seebold ABSTRACT: A driving circuit for producing percussion sound employed in an electronic musical instrument is composed of a plurality of circuit branches each of which consists of a capacitor and a resistor connected in parallel, a diode having the conductivity direction coincident with the charging current into the capacitor, and a normally opened switch interlinked with a corresponding key on the keyboard, all connected in series, the number of the circuit branches being substantially equivalent to the number of the keys on the keyboard, all of the plurality of circuit branches being further connected in parallel, one terminal of thus formed parallel circuit being connected with one end of a power source, the other terminal of the parallel circuit being connected through a resistor to the other end of the power source, whereby, when any one of the keys is depressed and the corresponding switch is closed, a charging current flows into the corresponding capacitor and a trigger signal is obtained from the junction point of the capacitor and the resistor connected to the other end of the power source.

PATENTEUJANIIS m1 3, 557,296.

' E U H PRIOR ART INVENTOR YASuNofi-i Hid 4 ATTORNEYS BACKGROUND or THE INVENTION This invention relates generally to a percussion sound producing circuit, and more specifically to a driving circuit for driving an envelope-forming circuit forobtaining percussion sound in cooperation with the keyboard of an electronic musical instrument.

A typical organization of a heretofore employed driving circuit for obtaining percussion sounds is illustrated in FIG. I of the accompanying drawing which will be described hereinafter. When any oneof double-throw switches 1,! u, Ib, interlinked with each of the keys on the keyboard is closed, one of capacitors 2, 2a, 2b, connected with the switch is further connected with a resistor 5, and charging current is passed into the capacitor through the resistor 5 and another resistor 6 from a power source 10.

The flow of the charging current into the capacitor causes a voltage drop across the resistor 6, and the thus created trigger pulse is furnished through a coupling capacitor 7 to the input circuit of an envelope-forming circuit 8. l

However, in the above described conventional driving circuit, when several of other keys have been depressed beforehand, if another key is newly depressed, the capacitors coo responding to the aforementioned several keysand having been charged as described above will be connected in parallel with the newly connected capacitor. As a result, the charging current for the newly. connected capacitor will be partly furnished from these previously charged capacitors, and the current passing through the resistor R6 will be decreasedby an amount corresponding the number, of keys previously depressed. Thus, the trigger signal obtained fromthe junction point between the resistors 5 and 6 cannot have a sufficient strength, and the envelope forming circuit cannot be driven appropriately. 1

Furthermore, because changeoverswitches must-be em ployed in this kind of circuit, the construction of the switching portion of the driving circuit tends to become of complicated nature. I

SUMMARY OF THE iNVENTION Therefore, the principal object of the invention is to provide a novel organization of the driving circuit wherein all of the drawbacks as described above can be completely overcome.

Another object of this invention is to provide an improved driving circuit to be used with an envelope-forming circuit for obtaining percussion sounds, wherein the trigger input pulse for the envelope-forming circuit can be of a sufficient strength regardless of the number of keys depressed beforehand.

Still another object of this invention is to provide a novel ty e of driving circuit for obtaining percussion sounds, wherein the switches interlinked with the keyboard of the musical instrument can be of a simplest construction.

These and other objects of the present invention can be achieved by an improved type of the driving circuit employed in an electronic musical instrument for obtaining percussion sounds, a said circuit comprising aplurality of branch circuits each of which has a capacitor and a resistor connected in parallel, a diode having the normal conducting direction coincident with the direction of the charging current into the capacitor, and a normally opened switch interlinked with a corresponding key on the keyboard, all connected in series, all of the plurality of branch circuits further connected in parallel, one terminal of the thus obtained parallel circuit being connected with one end of a power source, the other terminal of the parallel circuit being connected to the other end of the power source through a resistor, whereby a trigger signal is obtained from a capacitor connected with a junction point between the other terminal of the parallel circuit and the resistor.

The invention will be more fully understood from the following detailed description with respect to a preferred embodiment thereof, when read in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing: FIG. 1 is a schematic circuit diagram showing the organization of the conventional driving circuit for obtaining a percus- DETAILED DESCRIPTION A driving circuit for obtaining percussion sounds according V to the present invention will now be described in detail with.

reference to FIG. 2. In the drawing, it is seen that a capacitor 2 and a resistor 3 connected in parallel, a diode 4 disposed in a direction coincident with that of the charging current flowing into the capacitor 2, and a normally opened switch I are connected in series so that a series connected circuit branch is obtained.

Such series connected circuit branches of a number corresponding to the number, of keys on the keyboard are connected in parallel, and, in this case, the capacitance of the capacitors 2, 2a, 2 b, included in each of the series connected circuit branches and the resistance of the resistors 5 and 6 and the capacitance'of a coupling capacitor 7 are all selected to be optimum values so that an appropriate triggering of an envelope-forming circuit 8 is obtained.

Likewise, the resistance values of resistors 3, 3a, 3b, included in individual series connected circuit branches are selected to be values sufficiently larger than the resistance of the resistors 5 and 6 so that the time-constants obtained together with the capacitors'Z, 2a, 2b, are nearly equal to 50 msec. This value must be sufficiently smaller than the repetition'period of the key depression and sufficiently larger than the resistance values of the resistors 5 and 6.

It'should be noted that the resistors 5, 6 are constituting a voltage divider circuit and, for this reason, the resistor 5 is not essential and may be omitted. The envelope-forming circuit 8 includes, for instance, a monostable multivibrator and thereby generates pulse signals of a proper waveform, and a subsequent oscillation circuit or percussion sound switching circuit (not shown) are driven by the envelope-forming circuit. In this case, the oscillation circuit may be a pulsed oscillation of a conventional type which is in a state of rest when no trigering (pulse) signal is supplied and assumes an oscillating state when a triggering (pulse) signal is introduced, andthe switching circuit may be of a conventional one such as a transistor keyer to which is always supplied a percussion sound signal, but which is in cutoff state'when no triggering (pulse) signal is fed and becomes conducting when a triggering (pulse) signal is fed.

The operation of the driving circuit according to the present invention will now be described.

When the switch 1 is closed by depressing a key on the keyboard, a charging current for the capacitor 2 is passed through the resistors 5, 6 and a trigger pulse created across the resistors are furnished to the envelope-forming circuit 8 through the coupling capacitor 7.

Since the resistance of the resistor 3 is high, the current passing through the resistors 5, 6 is promptly attenuated and brought back to its original value of substantially zero.

If another key corresponding to, for instance, a switch la is depressed, the switch in is thereby closed. Since -no charging current for the capacitor 2a is allowed to flow from the previously charged capacitor 2' because of" the existence of the diode 4, almost all of the charging current flowing into the capacitor 2a passes through the resistors 5, 6, and another trigger pulse is again created at the junction point of the resistors 5 and 6.

It will be apparent from the above description that, even in the case when a plurality of keys have been previously depressed and a key is newly depressed, a trigger pulse of equivalent amplitude may be obtained regardless of the existence of the previously depressed keys. That is, each time a key is depressed, atrigger pulse of equivalent amplitude is always applied to the envelope-forming circuit without having any relation to the number of keys previously depressed, and the possibility oi"erroneous operation is thereby completely eliminated.

lclaim:

1. In a driving circuit to be used in an electronic musical instrument for obtaining percussion sounds wherein a plurality of branch circuits,-each of which includes a capacitor and a switch interlinked with a key on the keyboard of the instrument, are connected in parallel, a first terminal of the thus obtained parallel connected circuit is connected with an end ofa power source, a second terminal of said parallel connected circuit is further connected with the other end of said power source through a voltage dividing resistor, and a trigger signal is obtained from a terminal of said voltage-dividing resistor upon depression of a key, the improvement wherein each of said branch circuits comprises a resistor parallely connected with said capacitor, a unidirectonal element and a switching element both connected in series with said parallely connected capacitor and a resistor, whereby a cross current between the branch circuits is eliminated, and theamplitude of the trigger signal is stabilized. v

2. A driving circuit as defined in claim 1 wherein said unidirectional element is a diode the conductivity direction of which is coincident with the direction of the charging current flowing into the capacitor includedin the same circuit branch.

3. A driving circuit as defined in claim 1 wherein said switching element is a normally opened single-throw, single: pole switch.

4. A driving circuit as defined in claim 1 wherein said resistor parallely connected with said capacitor is of sufficiently high resistance but producing a time-constant of approximately 50 msec. together with said capacitor. 

1. In a driving circuit to be used in an electronic musical instrument for obtaining percussion sounds wherein a plurality of branch circuits, each of which includes a capacitor and a switch interlinked with a key on the keyboard of the instrument, are connected in parallel, a first terminal of the thus obtained parallel connected circuit is connected with an end of a power source, a second terminal of said parallel connected circuit is further connected with the other end of said power source through a voltage dividing resistor, and a trigger signal is obtained from a terminal of said voltage-dividing resistor upon depression of a key, the improvement wherein each of said branch circuits comprises a resistor parallely connected with said capacitor, a unidirectonal element and a switching element both connected in series with said parallely connected capacitor and a resistor, whereby a cross current between the branch circuits is eliminated, and the amplitude of the trigger signal is stabilized.
 2. A driving circuit as defined in claim 1 wherein said unidirectional element is a diode the conductivity direction of which is coincident with the direction of the charging current flowing into the capacitor included in the same circuit branch.
 3. A driving circuit as defined in claim 1 wherein said switching element is a normally opened single-throw, single-pole switch.
 4. A driving circuit as defined in claim 1 wherein said resistor parallely connected with said capacitor is of sufficiently high resistance but producing a time-constant of approximately 50 msec. together with said capacitor. 